You could set up a proportion to figure out the anwer. 15 hurdles/60%=X hurdles/100%. Cross multiply, 1500=60x. Divide by 60, 25=X=total amount of hurdles. Hope this helps!
For this expression I guessed I would use subtraction because when you subtract Kimiko's miles to Celeste's miles you could see how much faster Kimiko was than Celeste.